Vaults and safes have long been used to securely store articles. Such secure repositories are typically used in a bank to protect currency, negotiable paper, and safety deposit boxes. Typically, these vaults include walls, ceilings and floors made of a hardened metal outer layer backed by a thick layer of fire resistant material such as concrete. Sometimes this fire resistant material is further backed by another layer of hardened metal to provide a formidable barrier to unauthorized entry or breakage. Three of the walls, the ceiling, and the floor of the vault are encased within a reinforced concrete structure that leaves one wall exposed. This wall is provided with a framed opening in which a door is hung to provide access to the vault chamber enclosed within the walls, ceiling and floor of the vault.
The door to such a typical vault usually includes a hardened metal form having a front and four sides connected around the periphery of the front. This hardened metal form is filled with a fire resistant material. The door is hung within the framed opening on hinges mounted along one side of the door. Vertically mounted along the door edge opposed to the hinges is a lock bar. The lock bar is mounted in sliding relation to the vault door to throw or extend a portion of the lock bar beyond the edge of the vault door in a first position and to retract the lock bar within the periphery of the door in a second position. When the lock bar is in the first or thrown position and the door is closed, the lock bar portion extending beyond the door periphery lies rearward and adjacent the framed opening within the vault chamber to prevent the opening of the vault door. When the lock bar is slid to the second position to withdraw the lock bar within the periphery of the door, the door may be opened to provide access to the vault chamber.
The lock bar is connected to a cam and rod which extends through the door to a handle located on the front of the door. The handle is rotatably mounted so that by turning the handle the lock bar is moved from the first position to the second position to lock and unlock the vault door. Also mounted to the front of the door is a rotary dial of a combination lock that is connected to a rod that extends through the plate and fire resistant material to a set of tumblers and/or solenoids that control a blocking member. The end of the blocking member distal from the lock abuts the lock bar. When the vault door is closed and locked, the combination lock holds the blocking member against the lock bar to prevent the lock bar from sliding to the unlock position. By dialing in a combination to align the tumblers, the combination lock permits the blocking member to yield to the sliding of the lock bar so the door may be unlocked.
While this vault construction effectively protects the stored articles when it is locked, difficulties arise when the vault is left opened. One problem is the locking of employees within the safe either accidentally or intentionally such as when the bank or other institution is robbed. To prevent this from occurring, day locks have been designed which make the locking of the vault door without knowledge of the combination more difficult. These day locks secure the lock bar in the thrown position so the door cannot be closed within the framed opening. While such a daylock design prevents closure of the vault door after the door is opened, any attempt to close the door causes a collision between the lock bar and door frame which may result in damage to both elements.
Another daylock design holds the lock bar in a retracted position but automatically releases the lock bar when the vault door is closed to permit the locking of the door. Such a daylock effectively holds the locking bar while the door is open but anyone simply closing the door can lock employees within the vault.
What is needed is a day lock that keeps the lock bar in a retracted position once the lock bar is withdrawn and cannot be deactivated by an unauthorized person irregardless of vault door position.
Another feature added to vault doors to improve their effectiveness is a relock feature. Relocks are mechanisms which secure the lock bar in the locked position in response to an attack on the combination lock. Such a mechanism denies a burglar entry to the vault even though the burglar defeats the combination lock. Known types of relock mechanisms are activated by a frangible element located in the vicinity of the combination lock or by displacement of the combination lock itself. Both of these types of relocks present problems in their utilization. Those relocks incorporating frangible elements suffer from premature breakage of the frangible element stressed by vibrations occurring during operation of the vault door or other environmental stresses such as temperature cycling which weaken the element. Relocks which respond to the displacement of the combination lock are ineffective for attacks made through the door directly upon the blocking member in an effort to circumvent the relock mechanism.
What is needed is a relock mechanism that reduces the chances for a premature triggering of the relock and that is activated from attacks on areas of the door other than the combination lock.